Talc-filled TPOs can be used in injection molding applications, and other applications requiring a balance of rigidity, impact resistance at temperatures down to about −30° C., resistance to scratching and marring, and resistance to deformation at temperatures of about 100° C. The flex modulus for these grades of TPOs is typically between about 100,000 and 200,000 pounds per square inch (psi), and the heat of deflection temperature (HDT) is typically below about 110° C.
There is a continuing interest to replace conventional resins, such as polycarbonate based resins and polystyrene based resins with polyolefin alternatives. Several polypropylene compositions are described in the following patents or applications. U.S. Pat. No. 6,759,475 describes a resin composition based on crystalline polypropylene, which includes: (a) 3-65 weight percent (wt %) of a component soluble in para-xylene at 23° C. (the amorphous phase), (h) 35-97 wt % of a component soluble in para-xylene at 135° C., and insoluble in para-xylene at 23° C. (the high crystalline polypropylene phase), and (c) 0-30 wt % of a component insoluble in para-xylene at 135° C. (the filler). The component (a), soluble in para-xylene at 23° C. is composed substantially of an elastomeric constituent (a1) having a content of styrene, or its derivative, in the range of 0-35 wt %, and an intrinsic viscosity (η) in the range of 0.1-5 decaliters per gram (dl/g). The component (b), soluble is para-xylene at 135° C., and insoluble in para-xylene at 23° C., is composed substantially of a crystalline polypropylene constituent (b1) having an isotactic pentad proportion (mmmm) of 97 percent or higher, a molecular weight distribution (Mw/Mn or MWD) of 6 or higher, and a molecular weight distribution (Mz/Mw) of 6 or higher. The component (c), insoluble in para-xylene at 135° C., is composed substantially of filler (c1).
U.S. Pat. No. 6,964,997 describes a propylene resin composition that has good molding abilities and a good balance of physical properties as well as a good appearance, lower gloss and scratch resistance. These compositions can be used for interior car parts (for example, see abstract). The polypropylene resin composition comprises the following components; a crystalline homopolypropylene having MFR of 500 to 3,000 grams per 10 minutes (g/10 min); a polypropylene consisting of a crystalline homopolypropylene and an ethylene-propylene copolymer rubber having 45 to 80 percent, by mass, of a ethylene content; a polypropylene, consisting of a crystalline homopolypropylene and an ethylene-propylene copolymer rubber having 25 percent, by mass, or more, to below 45 percent, by mass, of a ethylene content; and an ethylene-α-olefin copolymer rubber (for example, see abstract).
U.S. Pat. No. 6,660,797 describes a propylene-based composition for molded polypropylene resin articles, excellent in resistance to scratching and moldability, and well-balanced properties between high rigidity and high impact strength, and also provides a method for molding the above propylene-based composition, to provide high-performance industrial parts and automobile parts, and in particular automobile interior parts (for example, see abstract). An example propylene-based resin composition contains the following components (A) and (B), as described below (for example, see column 2, lines 14-49). Component (A) is a propylene-based resin composed of the following components (a1), (a2) and (a3); 90 to 40 wt %: (a1) propylene/ethylene block copolymer, composed of 60 to 83 wt % of crystalline propylene homopolymer component (a1-1 unit) and 17 to 40 wt % of ethylene/propylene random copolymer component (a1-2 unit), containing 30 to 52 wt % of ethylene, and having a weight-average molecular weight of 230,000 to 600,000; and having a MFR (230° C., 2.16 kilograms (kg)) of 15 to 150 g/10 min, and number of gels of 100, or less, for those having a size of 50 microns (μm), or more, in the molded article of 25 centimeters squared (cm2, area) and 0.5 millimeters (m, thickness); 100 weight parts; (a2) talc having an average particle size of 0.5 to 15 μm; 0 to 200 weight parts; (a3) ethylene/α-olefin copolymer rubber, containing 20 to 50 wt % of α-olefin of 3 to 8 carbon atoms and having a MFR (230° C., 2.16 kg) of 0.3 to 100 g/10 min; 0 to 20 weight parts. Component (B) is a propylene-based resin material, composed of the following components (b1) and (b2); 10 to 60 wt %; (b1) propylene homopolymer or propylene/ethylene block copolymer, having a component insoluble in ortho-dichlorobenzene at below 120° C., accounting for 8 wt % or more of the component insoluble at below 100° C., when fractionated with ortho-dichlorobenzene as the solvent, and the component insoluble at below 100° C. has a weight-average molecular weight of 200,000 or more and a MFR (2.30° C., 2.16 kg) of 0.3 to 70 g/10 min; 15 to 80 weight parts; and (b2) talc or wollastonite having an average particle size of 0.5 to 15 μm; 20 to 85 weight parts (for example, see column 2, lines 14-49).
Additional polypropylene compositions are described in U.S. Pat. Nos. 5,286,776 and 6,667,359. Other polyolefin compositions and fabricated articles, such as automotive parts, prepared from the same, are described in U.S. Patent Application Publication Nos: 2005/0029692, 2004/0188885 and 2004/0094986. U.S. Patent Application Publication Nos. 2005/0272858 (see also WO 2004/033509) and 2004/0122196 describe additional propylene-based polymers and compositions. However, the compositions disclosed in these references, and those discussed above, are complex and costly due to the number of polymeric components in each composition and/or do not meet one or more desired rheological, mechanical or thermal properties of the inventive compositions described herein. Moreover, several of the compositions disclosed in these references require a polypropylene/(ethylene/polypropylene) heterophasic rubber, which is not advantageous for low temperature impact properties.
WO 2006/002436 describes compositions comprising (i) a crystalline, isotactic propylene homopolymer, (ii) an ethylene/α-olefin elastomeric impact modifier, and (iii) a reinforcing grade of filler, e.g., talc. The crystalline isotactic propylene homopolymer has a flex modulus greater than 1930 MegaPascal (MPa) and a HDT of greater than 100° C. The ethylene/α-olefin elastomeric impact modifier has a glass transition temperature (Tg) of less than −30° C. and a tan delta measured at 0.1 rad/s at 190° C. of less than 2. The filler has a HUT reinforcing efficiency of at least 2. The composition has an HDT of greater than 100° C., a flex modulus of greater than 1930 MPa, and a total energy absorption during impact at −30° C. of less than 20 ft-lb-f (27.12 N-m or J).
There is a continuing need for low cost polyolefin compositions, simple in polymeric formulations, and which can be used to form manufactured parts, such as injection molded parts, that have excellent mechanical and thermal properties. There is a further need for filled TPO compositions that can be used to form reinforced, light weight articles of manufacture, such as light-weight injection molded parts. There is also a need for such compositions that can be used to form articles of manufacture with improved low temperature performance properties. These needs and others are satisfied by the following invention.